Identification and optimization of pyridazinones as potent and selective c-Met kinase inhibitors

In a high-throughput screening campaign for c-Met kinase inhibitors, a thiadiazinone derivative with a carbamate group was identified as a potent in vitro inhibitor. Subsequent optimization guided by c-Met-inhibitor X-ray structures furnished new compound classes with excellent in vitro and in vivo profiles. The thiadiazinone ring of the HTS hit was first replaced by a pyridazinone followed by an exchange of the carbamate hinge binder with a 1,5-disubstituted pyrimidine. Finally an optimized compound, 22 (MSC2156119), with excellent in vitro potency, high kinase selectivity, long half-life after oral administration and in vivo anti-tumor efficacy at low doses, was selected as a candidate for clinical development.